macros with expired revoked signature????

i run windows XP and word 2002when i open word i get a dialogue box that says..."This file contains macros with an expired or revoked signature. since you are running under high security level, these macros will be disabled." then another which says....."The macros in this project are disabled. please refer to the online help or documentation of the host application to determine how to enable macros."i did open and alter a word document on a floppy disk from a friend who required an update to a CV which is when i first notcied anything to do with macrosall my applications were fine before this.....now i cant use my netobjects fusion programme without it crashing with the same problem....i looked to change the scurity level from high but im not sure if this will be a good idea with all the viruses aboutcan you help pleasewilliam